Architecture and methods for coexistence of wireless radios having differing protocols

ABSTRACT

Embodiments of systems and methods for the coexistence of wireless radios having differing protocols are generally described herein. Other embodiments may be described and claimed. In some embodiments systems and methods for synchronizing clocks between two radios, and using a signal to notify one of the radios to refrain from transmitting for a timeperiod are described.

TECHNICAL FIELD

The present inventive subject matter pertains to wirelesscommunications. Some embodiments may pertain to architecture and methodsfor coexistence of wireless radios having differing protocols.

BACKGROUND

With the increasing availability of wireless technology andconnectivity, devices carrying multiple radios will not be uncommon. Asone example, combinations of Bluetooth, WiFi and WiMAX technologies maybe made available on future computation and communication platforms suchas laptops and handheld devices. These types of platforms may beequipped with multiple co-located radios. Such platforms may be referredto as a Multi-Radio Platforms (MRPs). MRPs may include the co-locationof Bluetooth, WiMAX and even WiFi radios to accommodate various uses andconveniences. One typical usage scenario for the multiple radiosincludes the MRP relaying voice traffic between its WiMAX and Bluetoothlinks. A Bluetooth headset may connect to the MRP via a Bluetooth linkand the MRP, at the same time, may maintain an active WiMAX VoIP sessionwith WiMAX base station.

Bluetooth and WiMAX may operate in overlapping or adjacent frequencybands and possibly suffer from interference when they operate atsubstantially overlapping time instants. Interference may occur, forexample, due to physical proximity and radio power leakage. Thefollowing interferences, also referred to as BT and WiMAX collisions canoccur:

1. When Bluetooth transmission overlaps with WiMAX receiving in timedomain at the MPR, WiMAX receiving can suffer; and

2. WiMAX transmissions can also interfere with Bluetooth receivingoperations at the MPR when they overlap in time.

3. Similarly, interference may also be caused when WiMAX transmissionand Bluetooth transmission operations overlap in time.

Thus, there are general needs for system architecture to allowconcurrent communications between devices implementing differentprotocols with reduced interference.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a radio coexistence system according tovarious embodiments;

FIG. 2 is a block diagram of an example radio coexistence systemaccording to various embodiments;

FIG. 3 is a flow diagram illustrating a method in accordance withvarious embodiments;

FIG. 4A is a block diagram of an example multi-radio coexistence systemaccording to various embodiments; and

FIG. 4B is a block diagram of another example multi-radio coexistencesystem according to various embodiments.

DETAILED DESCRIPTION

The following description and the drawings sufficiently illustratespecific embodiments of the inventive subject matter to enable thoseskilled in the art to practice them. Other embodiments may incorporatestructural, logical, electrical, process, and other changes. Examplesmerely typify possible variations. Individual components and functionsare optional unless explicitly required, and the sequence of operationsmay vary. Portions and features of some embodiments may be included in,or substituted for those of other embodiments. Embodiments of theinventive subject matter set forth in the claims encompass all availableequivalents of those claims. Embodiments of the inventive subject mattermay be referred to herein, individually or collectively, by the term“invention” merely for convenience and without intending to limit thescope of this application to any single invention or inventive conceptif more than one is in fact disclosed.

FIG. 1 is a block diagram of a radio coexistence system according tovarious embodiments. The system 100 comprises a first radio 102including a first clock 104, a second radio 106 including a second clock108, a coexist controller 110, an active link 112 and a synchronizationlink 114.

The first radio 102 may operate as a transceiver being able to transmitand receive wireless signals on one of a number of possible wirelessnetworks, using various transmission protocols. The first radio mayinclude a first clock 104 which may be used to regulate transmissions byproviding consistent timing. The second radio 106 may likewise operateas a transceiver being able to transmit and receive wireless signals onone of a number of possible wireless networks using various transmissionprotocols. The second radio 106 also may employ a second clock 108 toregulate transmission timing. Depending on the wireless networks andprotocols used by the first radio 102 and the second radio 106,interference between the two radios may occur. Interference is morecommon when the first radio 102 and the second radio 106 operate withinthe same or nearby frequency bands.

By allowing the first radio 102 and the second radio 106 to communicateand adjust, interference may be reduced. A coexist controller 110 may beutilized to coordinate the communication between the radios. The coexistcontroller 110 may be integrated into the first radio 102 or mayoptionally be external to the first radio 102. The coexist controller110 may have a connection to the first clock 104, and may be able todetermine when the first radio 102 is transmitting or receiving. Theconnection may be a wired connection, an optical connection, a wirelessconnection, or other connection types. With information from theconnection with the first clock 104, the coexist controller 110 may beable to transmit a signal over a synchronization link 114 to the secondradio 106. The signal over the synchronization link 114 may allow thesecond radio 106 to synchronize the second clock 108 with the firstclock 104. The second radio 106 may synchronize the second clock 108 byadjusting the second clock 108 to begin a clock cycle in sync with thesignal sent over the synchronization link 114. An optional offset mayadditionally be employed when synchronizing the second clock 108 withthe first clock 104 as needed, allowing the second clock 108 to besynchronized with an offset with respect to the first clock 104.

The coexist controller 110 may also transmit a signal over the activelink 112. The signal transmitted over the active link 112 may notify thesecond radio 106 that the first radio 102 is either transmitting orreceiving. Upon receiving the signal over the active link 112, thesecond radio will refrain from transmitting. The signal sent over theactive link 112 may last for a finite timeperiod. Once the timeperiodhas expired and the signal is cleared, the second radio 106 may transmitagain. If the system 100 is configured to avoid interference betweenreceptions from the first radio 102 and transmissions from the secondradio 106, the signal sent by the coexist controller 110 over the activelink 112 will notify the second radio 106 that the first radio isreceiving. Thus the second radio 106 will not transmit while the firstradio 102 is receiving, and interference may be avoided. Alternatively,if the system 100 is configured to avoid interference betweentransmissions from the first radio 102 and transmissions from the secondradio 106, the signal sent by the coexist controller 110 over the activelink 112 will notify the second radio 106 that the first radio istransmitting. Thus the second radio 106 will not transmit while thefirst radio 102 is transmitting, and interference may be avoided.

FIG. 2 is a block diagram of an example radio coexistence system 200according to various embodiments. The system 200 comprises a WiMAX radio202, a WiMAX clock 204, a WiMAX driver 206, a Bluetooth radio 208, aBluetooth clock 210, auxiliary links 212, a coexist controller 214, asynchronization link 216, and an active link 218.

This example implementation demonstrates a coexistence system 200 with aWiMAX radio 202 and a Bluetooth radio 208. Although this and otherembodiments will be described with respect to Bluetooth and WiMAX radiosand protocols, the scope of the invention is not limited in this respectand may apply to any communication radios and protocols that potentiallyinterfere.

The WiMAX radio 202 includes a WiMAX clock 204 to allow for consistenttransmission timing and synchronization with WiMAX base stations.Similarly, the Bluetooth radio 208 includes a Bluetooth clock 210 toallow for consistent transmission timing. As described above, in orderto facilitate coexistence and allow for communication between theradios, a coexist controller 214 may be used. The coexist controller 214may be internal or external to the WiMAX radio 202, but nevertheless incommunication. The coexist controller 214 may access or communicate withthe WiMAX clock 204 in order to create a FRAME_SYNC signal to betransmitted over the synchronization link 216 to the Bluetooth radio.The FRAME_SYNC signal may be a periodic signal created from the WiMAXclock 204. The periodic FRAME_SYNC may optionally be offset apredetermined amount from the WIMAX clock 204. Different offset amountsmay be used with different wireless frame sizes associated with theWiMAX radio 202 and the Bluetooth radio 208. Additionally, differentoffset amounts may be used with different working modes or interferencescenarios. When the FRAME_SYNC signal is received at the Bluetooth radio208 over the synchronization link 216, the Bluetooth clock 210 may besynchronized with the signal. This may effectively synchronize theBluetooth clock 210 with the WiMAX clock 204, or at least align the twowith a predetermined offset.

In general, there may be four types of WiMAX/Bluetooth interference: (1)WiMAX transmission (TX) interferes Bluetooth reception (RX), (2) WiMAXTX interferes Bluetooth TX, (3) Bluetooth TX interferes with WiMAX RX,(4) WiMAX RX conflicts with Bluetooth RX. The interference scenario of asystem can be a combination of those four. Two working modes coveringthese interference types may b described as: “TX/RX-conflict mode” and“TX/TX-conflict mode”. TX/RX-conflict mode refers to the combination oftype (1) and (3); TX/TX-conflict mode refers to the combination of type(2) and (4) (for example, when WiMAX TX signal is much stronger than theBluetooth TX signal, WiMAX TX can severely affect Bluetoothtransmissions due to power amplifier (PA) distortion andinter-modulation).

Depending on whether the system 200 is dealing with TX/RX-conflict modeor TX/TX-conflict mode, the coexist controller 214 may need to know whento send a WIMAX_ACT signal over the active link 218 to the Bluetoothradio 208. The WIMAX_ACT signal notifies the Bluetooth radio 208 whenthe WiMAX radio 202 is “active”, and the Bluetooth radio 208 should nottransmit. In the case of TX/RX-conflict mode, the WIMAX_ACT signalshould be sent when the WiMAX radio 202 is receiving. In the case ofTX/TX-conflict mode, the WIMAX_ACT signal should be sent when the WiMAXradio 202 is transmitting. The WiMAX driver 206 may instruct the coexistcontroller 214 as to the present mode of operation and thus when theWIMAX_ACT signal should be sent over the active link 218. While theWIMAX_ACT signal notifies the Bluetooth radio 208 not to transmit, theabsence of a WIMAX_ACT signal on the active link 218 may alert theBluetooth radio 208 to refrain from reception or receiving incomingtransmissions. This would not only avoid WiMAX interference withBluetooth transmissions, but also interference with Bluetooth receptionsin accordance with either TX/RX-conflict mode or TX/TX-conflict mode.Additionally, an offset in the FRAME_SYNC signal sent over thesynchronization link 216 may be determined based on whether the system200 is dealing with TX/RX-conflict mode or TX/TX conflict mode. For aWiMAX radio 202 transmitting wireless frames of 5 ms duration, and aBluetooth radio 208 transmitting in SCO intervals having six 0.625 msslots, the WiMAX radio 202 wireless frame would have the equivalent of 8slots. With this configuration, an example offset between the start ofthe Bluetooth SCO interval and the start of the WiMAX frame forTX/RX-conflict mode may be a 1 slot offset. An example offset forTX/TX-conflict mode may be a 0 slot offset, or no offset. Differingoffsets may yield differing interference avoidance results.

Many current Bluetooth radios 208 may be setup for coexistence with WiFior other like devices. The Bluetooth radio 208 may use varioustechniques, examples of which are described in the IEEE 802.15.2specification. These techniques may use one or more auxiliary links 212to provide attempted interference mitigation. These auxiliary links 212may be used alone or in conjunction with the active link 218.Embodiments including more than two radios and the use of the auxiliarylinks 212 are described in more detail with reference to FIGS. 4A and4B.

Additionally, Bluetooth radio 208 may utilize one of various Bluetoothlink configurations. Link configurations include EV3, HV3, HV1, andothers. In the case that the Bluetooth radio 208 uses a Bluetooth EV3link, it may follow the standard retransmission policies includingretransmitting a failed transmission during a retransmission window. Inthis circumstance, when the Bluetooth radio 208 refrains fromtransmitting due to a WIMAX_ACT signal on the active link 218, theBluetooth radio 208 may treat that transmission as a failedtransmission. The Bluetooth radio 208 may retransmit the potentiallyinterfering transmission in the retransmission window, when theWIMAX_ACT signal is no longer present on the active link 218. Thisretransmission method may apply for a number of other wireless radiosand associated transmission protocols. A transmission that is restrictedfrom being transmitted due to activity on another radio may berescheduled and retransmitted at a later time. Additionally, receptionsthat may not be available to be received because of interference fromanother co-located radio or radios may be rescheduled and polled ifnecessary for retransmission at another time.

FIG. 3 is a flow diagram illustrating a method 300 in accordance withvarious embodiments. The method 300 begins with a first radio receivinga FRAME_SYNC signal from a co-located second radio (302). The FRAME_SYNCsignal may be any signal which is periodic and based on the secondradio's clock signal. The FRAME_SYNC signal may be aligned with thesecond radio's clock signal or may be offset by an amount. Depending onthe mode of operation for the type of interference to be avoided,various offset amounts may be utilized. The first radio may use theFRAME_SYNC signal to synchronize its clock (304). By synchronizing withthe FRAME_SYNC signal, the first radio is essentially aligning its clockwith the clock in the second radio, plus or minus any offset.

In order to begin a transmission, the first radio may determine whetheror not it is receiving an _ACT signal (block 306). The _ACT signal maybe any signal sent from the second radio to the first radio indicatingthat the second radio is performing an action. The action, for example,may be the second radio transmitting or receiving. According to someembodiments, the _ACT signal may be described as a WIMAX_ACT signal, aWLAN_ACT signal, or other notations. If the first radio determines thatit is not currently receiving an _ACT signal, the first radio is okay totransmit data (block 308). Alternatively, if the first radio determinesthat it is currently receiving an _ACT signal, the first radio mayrefrain from transmitting (block 310). If the first radio is notcurrently receiving an _ACT signal, and it is okay to transmit (block308), it may proceed to transmit (block 312) within its wireless frameusing the synchronized clock signal.

Additionally, according to various embodiments, when the first radiodetermines that it is not receiving an _ACT signal, and it is okay totransmit (block 308), it may refrain from receiving. Similarly, when thefirst radio determines that it is receiving an _ACT signal, and itrefrains from transmitting (block 310), it may determine it is okay toreceive.

FIG. 4A is a block diagram of an example multi-radio coexistence system400 according to various embodiments. The system 400 includes threeradios, a WiMAX radio 402, a Bluetooth radio 404, and a WiFi radio 406.The system 400 also includes a coexist controller 408, synchronizationlink 410, active link 412 and an OR gate 414.

As described above, the WiMAX radio 402 communicates with the coexistcontroller 408 to communicate with the Bluetooth radio 404. The coexistcontroller may use the synchronization link 410 to allow the clocks inthe Bluetooth radio 404 and in the WiMAX radio 402 to synchronize. Thecoexist controller 408 may also use the active link 412 to inform theBluetooth radio 404 when the WiMAX radio 402 is actively transmitting orwhen it is actively receiving. In the case of the system 400 of FIG. 4A,an additional radio is present, a WiFi radio 406. Standards andtechniques may be available for allowing the coexistence between theBluetooth radio 404 and the WiFi radio 406. Some Bluetooth radiosprovide a coexistence interface to support Packet Arbitration between aBluetooth radio 404 and a WiFi radio 406. Multiple variations of theBluetooth radio 404 to WiFi radio 406 coexistence interface (e.g.,2-wire, 3-wire or 4-wire interfaces) are available, and may work inconjunction with embodiments of the inventive subject matter.

The WiFi radio 406 may use the active link 412 or a similar link tonotify the Bluetooth radio that it is “active.” Being “active” may meanthat the WiFi radio 406 is transmitting, receiving, or performinganother function. The WiFi radio 406 may communicate with the Bluetoothradio 404 as it generally would, except that it may share the activelink 412 with the WiMAX radio 402 coexist controller 408. In order toshare the active link 412 to the Bluetooth radio 404 between the WiFiradio 406 and the WiMAX radio 402 coexist controller 408, an OR gate 414may be used. The OR gate 414 may have input connections coming from theWiFi radio 406 and from the coexist controller 408 associated with theWiMAX radio 402. The output of the OR gate 414 along the active link 412connects to the Bluetooth radio 404. Thus the OR gate 414 may allow theBluetooth radio 404 to receive signals over the active link 412 fromeither the coexist controller 408 or the WiFi radio 406.

In this way, the addition of the WiMAX radio 402, the coexist controller408 and the synchronization link 410 to communicate with the Bluetoothradio 404 may not affect the communications or operation of the WiFiradio 406.

FIG. 4B is a block diagram of another example multi-radio coexistencesystem 400 according to various embodiments. The system 400 of FIG. 4Bis similar to the system 400 of FIG. 4A, but includes a proxy 416instead of an OR gate 414 (FIG. 4A). The proxy 416 may contain thecoexist controller 408 according to various embodiments. The proxy 416may operate to generate signals to allow connected and co-located radiosto communicate. The proxy 416 may be connected to the WiMAX radio 402,the Bluetooth radio 404 and the WiFi radio 406. According to variousembodiments, the proxy may be hardware based, software based, a radiocontroller, a microprocessor, or a number of other devices.

The system 400 is an example implementation of an embodiment of theinventive subject matter. In the examples above, WiMAX, Bluetooth, andWiFi radios are used to illustrate embodiments with three differingwireless protocols. Other types of radios operating on various networksutilizing various protocols may be implemented within the scope of theinventive subject matter.

Although the system 400 is illustrated as having several separatefunctional elements, one or more of the functional elements may becombined and may be implemented by combinations of software-configuredelements, such as processing elements including digital signalprocessors (DSPs), and/or other hardware elements. For example, someelements may comprise one or more microprocessors, DSPs, applicationspecific integrated circuits (ASICs), and combinations of varioushardware and logic circuitry for performing at least the functionsdescribed herein.

In some embodiments, the communication systems and methods may beimplemented in accordance with specific communication standards, such asthe Institute of Electrical and Electronics Engineers (IEEE) standardsincluding the IEEE 802.16-2004 and the IEEE 802.16(e) standards forwireless metropolitan area networks (WMANs), as well as the IEEE 802.15standards for wireless personal area networks (WPANs) includingvariations and evolutions thereof, although the scope of the inventivesubject matter is not limited in this respect as the communicationsystems and methods may also be suitable for transmit and/or receivecommunications in accordance with other techniques and standards. Formore information with respect to the IEEE 802.16 standards, please referto “IEEE Standards for Information Technology—Telecommunications andInformation Exchange between Systems”—Metropolitan AreaNetworks—Specific Requirements—Part 16: “Air Interface for FixedBroadband Wireless Access Systems,” May 2005 and relatedamendments/versions. For more information with respect to the IEEE802.15 standards, please refer to “IEEE Standard for Informationtechnology—Telecommunications and information exchange betweensystems—Local and metropolitan area networks—Specific requirements. Part15.1: Wireless Medium Access Control (MAC) and Physical Layer (PHY)Specifications for Wireless Personal Area Networks (WPANs).”

In some embodiments, devices using the radios described above may beportable wireless communication devices, such as personal digitalassistants (PDAs), a laptops or portable computers with wirelesscommunication capability, web tablets, wireless telephones, wirelessheadsets, pagers, instant messaging devices, digital cameras, accesspoints, televisions, video gaming systems, medical devices (e.g., aheart rate monitor, a blood pressure monitor, etc.), or other devicesthat may receive and/or transmit information wirelessly. In someembodiments, a radio may operate using directional antennas,beam-forming antennas, omnidirectional antennas, multiple-inputmultiple-output (MIMO) antenna systems, adaptive antenna systems (AAS),diversity antennas, or other antenna configurations.

Some embodiments may be implemented in one or a combination of hardware,firmware, and software. Embodiments of the inventive subject matter mayalso be implemented as instructions stored on a machine-readable medium,which may be read and executed by at least one processor to perform theoperations described herein. A machine-readable medium may include anymechanism for storing or transmitting information in a form readable bya machine (e.g., a computer). For example, a machine-readable medium mayinclude read-only memory (ROM), random-access memory (RAM), magneticdisk storage media, optical storage media, flash-memory devices, andothers.

The Abstract is provided to comply with 37 C.F.R. Section 1.72(b)requiring an abstract that will allow the reader to ascertain the natureand gist of the technical disclosure. It is submitted with theunderstanding that it will not be used to limit or interpret the scopeor meaning of the claims. The following claims are hereby incorporatedinto the detailed description, with each claim standing on its own as aseparate embodiment.

1. A wireless communication device comprising: a first transceiver configured to transmit a WiMAX frame; and a second transceiver configured to transmit and receive within slots of a Bluetooth interval comprising six consecutive Bluetooth slots, and configured to refrain from transmitting and receiving from within slots that are not within a Bluetooth interval, wherein the first transceiver is operable to transmit a plurality of signals from a coexist controller associated with the first transceiver to the a second transceiver, one of the signals allowing the second transceiver to synchronize the Bluetooth interval with an offset with respect to a WiMAX frame, and one of the signals notifying the second transceiver of a timeperiod to refrain from transmitting a Bluetooth transmission, wherein the second transceiver is operable to delay the transmitting of the Bluetooth transmission until a retransmission window portion of the Bluetooth interval, the transmitting occurring after the timeperiod to refrain from transmitting the Bluetooth transmission; wherein the second transceiver is synchronized with the offset such that a start of at least one Bluetooth interval is one Bluetooth slot offset from a start of at least one WiMAX frame for a potential TX/RX conflict, the potential TX/RX conflict being when a WiMAX transmission would potentially interfere with a Bluetooth reception.
 2. The wireless communication device of claim 1, wherein the signals from the coexist controller are received over a wired connection, and wherein the second transceiver is further synchronized with the offset such that the start of at least one Bluetooth interval is a zero Bluetooth slot offset for a potential TX/TX conflict, the potential TX/TX conflict being when a WiMAX transmission would potentially interfere with a Bluetooth transmission.
 3. The wireless communication device of claim 1, wherein the second transceiver receives at least one of the signals from the coexist controller when the first transceiver is receiving.
 4. The wireless communication device of claim 3, wherein the signals allow the second transceiver to arrange transmissions to not temporally overlap with receptions by the first transceiver.
 5. The wireless communication device of claim 1, wherein the second transceiver receives at least one of the signals from the coexist controller while the first transceiver is transmitting.
 6. The wireless communication device of claim 5, wherein the signals allow the second transceiver to arrange transmissions to not temporally overlap with transmissions by the first transceiver.
 7. The wireless communication device of claim 1, further comprising a third transceiver; and an OR gate having inputs connected to the third transceiver and the coexist controller and having an output connected to the second transceiver, the OR gate to receive and send signals from the third transceiver and the coexist controller to the second transceiver.
 8. The wireless communication device of claim 1, further comprising a third transceiver; and a proxy connected to the first transceiver, the second transceiver and the third transceiver, the proxy including the coexist controller.
 9. The method of claim 1, one of the signals of the plurality of signals notifying the second transceiver to poll a Bluetooth transmitting device and cause a retransmission from the Bluetooth transmitting device to the second transceiver, wherein the second transceiver is operable to delay the poll and receiving of the retransmission from the Bluetooth transmitting device until the retransmission window portion of the Bluetooth interval, the receiving occurring after a timeperiod allocated for transmission of the WiMAX frame.
 10. A method for reducing interference comprising: receiving a synchronization signal from a first radio at a second radio, wherein the first radio is configured to transmit and receive WiMAX frames and the second radio is configured to transmit and receive within slots of a Bluetooth interval comprising six consecutive Bluetooth slots, and configured to refrain from transmitting and receiving from within slots that are not within a Bluetooth interval; synchronizing a Bluetooth interval from the second radio with the synchronization signal; wherein the synchronization signal is configured to cause the Bluetooth interval to be synchronized with respect to an offset from a WiMAX frame, such that a start of at least one Bluetooth interval transmitted by the second radio is one Bluetooth slot offset from a start of at least one WiMAX frame transmitted by the first radio for a potential TX/RX conflict; receiving an active signal from the first radio at the second radio, the active signal indicating a timeperiod to refrain from transmission; refraining from transmitting from the second radio during the timeperiod, the timeperiod including times when the first radio is receiving; and transmitting from the second radio during a retransmission window portion of the Bluetooth interval, the transmitting occurring after the timeperiod, wherein the potential TX/RX conflict is when a WiMAX transmission would potentially interfere with a Bluetooth reception.
 11. The method of claim 10, wherein the second radio is a Bluetooth radio.
 12. The method of claim 11, further comprising using a Bluetooth EV3 link; and following standard EV3 retransmission policies.
 13. The method of claim 12, wherein refraining from transmitting is treated as a failed transmission.
 14. The method of claim 10, wherein the synchronization signal is a periodic signal.
 15. The method of claim 10, wherein the second radio receives the active signal from the first radio when the first radio is receiving.
 16. The method of claim 10, wherein the second radio receives the active signal from the first radio when the first radio is transmitting.
 17. A radio comprising: a transmitter configured to operate in accordance with a Bluetooth transmission protocol and to transmit and receive within slots of a Bluetooth interval comprising six consecutive Bluetooth slots, and configured to refrain from transmitting and receiving from within slots that are not within a Bluetooth interval; a clock connected to the transmitter to regulate transmission timing; a synchronization link input to receive signals from a source to synchronize the clock, wherein Bluetooth intervals are synchronized with an offset with respect to WiMAX frames of the source, such that a start of at least one Bluetooth interval is one Bluetooth offset from a start of at least one WiMAX frame for a potential TX/RX conflict, the potential TX/RX conflict being when a WiMAX transmission would potentially interfere with a Bluetooth reception; and an active link input to receive signals from a source to alert the transmitter to refrain from transmitting until a retransmission window portion of a Bluetooth interval, the transmitting not overlapping with a transmission of a WiMAX frame of the source.
 18. The radio of claim 17, wherein the source is an external radio, the external radio using a second transmission protocol. pg,19
 19. The radio of claim 18, wherein the first transmission protocol is used on a broadband wireless network, and the second transmission protocol is used on a wireless personal area network. 